Definitive Ephemeris

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An ephemeris is a set of data that provides the assigned places of a celestial body (including a manmade satellite) for regular intervals. Definitive Ephemeris shows the position and velocity of the spacecraft at the time imagery is collected, and shows the position and velocity of the satellites in one-minute intervals.

Landsat 7 scenes were initially processed with predicted ephemeris shortly after acquisition, and were then reprocessed with Definitive ephemeris one to two days later. Section 5 of the Landsat 7 Data Users Handbook provides more technical information about Definitive Ephemeris and how it was used in Landsat 7 product generation.  Definitive ephemeris files are also available for Landsat 5 data. 

Definitive ephemeris files for Landsat 5 and Landsat 7 can be retrieved from the Definitive Ephemeris Search application. 

Landsat 8 and Landsat 9

Landsat 8 or Landsat 9 do not require definitive ephemeris, since the Payload Correction Data (PCD) for the satellites is very accurate. Telemetry information in the form of Two-Line Element (TLE) Set — which lists the orbital elements that describe the state (position and velocity) of each of the Landsat spacecrafts- is provided on the following pages: 

• Landsat 9:  https://www.n2yo.com/satellite/?s=49260
• Landsat 8: https://www.n2yo.com/satellite/?s=39084